U.S. patent application number 12/669443 was filed with the patent office on 2010-07-22 for hydrogen generation system, fuel cell system, and method for operation of hydrogen generation system.
This patent application is currently assigned to PANASONIC CORPORATION. Invention is credited to Seiji Fujihara, Yukimune Kani, Kensaku Kinugawa, Hidenobu Wakita.
Application Number | 20100183928 12/669443 |
Document ID | / |
Family ID | 42337206 |
Filed Date | 2010-07-22 |
United States Patent
Application |
20100183928 |
Kind Code |
A1 |
Fujihara; Seiji ; et
al. |
July 22, 2010 |
HYDROGEN GENERATION SYSTEM, FUEL CELL SYSTEM, AND METHOD FOR
OPERATION OF HYDROGEN GENERATION SYSTEM
Abstract
A hydrogen generating apparatus is provided that further
suppresses deterioration in capability of a converting catalyst in
raw material purge in a shutdown operation. The hydrogen generating
apparatus contains a raw material supplying device 101 that
supplies a raw material; a reforming device 111 that contains a
reformation catalyst and generates a hydrogen-containing gas from
the raw material through reformation reaction with the reformation
catalyst; a modifying device 121 that contains a modification
catalyst and decreases carbon monoxide in the hydrogen-containing
gas through shift reaction with the modification catalyst; a first
temperature detector 123 that detects a temperature of the
modification catalyst; and a controlling device 200, and the
controlling device 200 controls the raw material supplying device
101 to purge an interior of the converting device 121 with the raw
material when a detected temperature of the first temperature
detector 123 becomes a first threshold value, at which
deterioration of the modification catalyst with the raw material is
suppressed, or lower in a shutdown operation.
Inventors: |
Fujihara; Seiji; (Osaka,
JP) ; Kani; Yukimune; (Osaka, JP) ; Wakita;
Hidenobu; (Kyoto, JP) ; Kinugawa; Kensaku;
(Nara, JP) |
Correspondence
Address: |
MCDERMOTT WILL & EMERY LLP
600 13TH STREET, NW
WASHINGTON
DC
20005-3096
US
|
Assignee: |
PANASONIC CORPORATION
OSAKA
JP
|
Family ID: |
42337206 |
Appl. No.: |
12/669443 |
Filed: |
July 4, 2008 |
PCT Filed: |
July 4, 2008 |
PCT NO: |
PCT/JP2008/001800 |
371 Date: |
January 15, 2010 |
Current U.S.
Class: |
429/423 ;
422/110; 423/648.1 |
Current CPC
Class: |
C01B 2203/1223 20130101;
C01B 2203/1609 20130101; C01B 2203/1614 20130101; H01M 8/0618
20130101; Y02P 20/10 20151101; C01B 2203/0883 20130101; C01B
2203/107 20130101; C01B 2203/1241 20130101; H01M 8/0631 20130101;
C01B 2203/047 20130101; C01B 2203/1058 20130101; C01B 2203/1064
20130101; C01B 2203/1247 20130101; C01B 2203/0827 20130101; C01B
2203/0822 20130101; Y02E 60/50 20130101; C01B 3/384 20130101; C01B
2203/0283 20130101; C01B 2203/0811 20130101; C01B 2203/044
20130101; C01B 3/48 20130101; C01B 2203/146 20130101; C01B
2203/0233 20130101; C01B 2203/1619 20130101; C01B 2203/066
20130101 |
Class at
Publication: |
429/423 ;
422/110; 423/648.1 |
International
Class: |
H01M 8/18 20060101
H01M008/18; C01B 3/02 20060101 C01B003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 18, 2007 |
JP |
2007187275 |
Claims
1-14. (canceled)
15. A hydrogen generating apparatus comprising: a raw material
supplying device that supplies a raw material; a reforming device
that contains a reformation catalyst and generates a
hydrogen-containing gas from the raw material through a reformation
reaction with the reformation catalyst; a converting device that
contains a converting catalyst and decreases carbon monoxide in the
hydrogen-containing gas through shift reaction with the converting
catalyst; a first temperature detector that detects a temperature
of the converting catalyst; and a controlling device, the
controlling device controlling the raw material supplying device to
purge an interior of the converting device with the raw material
when a detected temperature of the first temperature detector
becomes a first threshold value, at which deterioration of the
converting catalyst with the raw material is suppressed, or lower
in a shutdown operation.
16. The hydrogen generating apparatus according to claim 15,
wherein the apparatus comprises a cooling device that cools the
converting catalyst, and the controlling device cools the
converting catalyst with the cooling device and performs the
control in a shutdown operation.
17. The hydrogen generating apparatus according to claim 15,
wherein the apparatus comprises a cooling device that cools the
converting catalyst, and the controlling device controls the
cooling device in such a manner that the detected temperature of
the first temperature detector becomes the first threshold value or
lower before purging an interior of the reforming device and the
interior of the converting device, with the raw material.
18. The hydrogen generating apparatus according to claim 15,
wherein the controlling device controls the raw material supplying
device to purge an interior of the converting device with the raw
material when a detected temperature of the first temperature
detector is the first threshold value or lower and is higher than a
dew point of a gas in the converting device.
19. The hydrogen generating apparatus according to claim 15,
wherein the apparatus comprises a second temperature detector that
detects a temperature of the reformation catalyst, and the
controlling device performs the control when a detected temperature
of the first temperature detector is the first threshold value or
lower, and a detected temperature of the second temperature
detector becomes a second threshold value, at which deterioration
of the reformation catalyst with the raw material is suppressed, or
lower.
20. The hydrogen generating apparatus according to claim 19,
wherein the apparatus comprises a heating device that heats the
reformation catalyst, and a cooling device that cools the
converting catalyst, and in a shutdown operation, the controlling
device stops the heating device and controls the cooling device in
such a manner that the detected temperature of the first
temperature detector becomes the first threshold value or lower at
the time when the detected temperature of the second temperature
detector becomes the second threshold value or lower or before the
time when it becomes the second threshold value or lower.
21. The hydrogen generating apparatus according to claim 16,
wherein the cooling device is a cooling fan.
22. The hydrogen generating apparatus according to claim 20,
wherein the cooling device is a cooling fan.
23. The hydrogen generating apparatus according to claim 15,
wherein the apparatus comprises a cooling device that cools the
converting catalyst, and a heating device that heats the
reformation catalyst, the heating device contains a fuel supplying
part that supplies a fuel for combustion and an air supplying part
that supplies air for combustion, and the air supplying part also
functions as the cooling device.
24. The hydrogen generating apparatus according to claim 15,
wherein the converting catalyst contains Cu and Zn.
25. A fuel cell system comprising: the hydrogen generating
apparatus according to claim 15, and a fuel cell that generates
electric power by using the hydrogen-containing gas supplied from
the hydrogen generating apparatus.
26. A method for operating a hydrogen generating apparatus, the
hydrogen generating apparatus including: a raw material supplying
device that supplies a raw material; a reforming device that
contains a reformation catalyst and generates a hydrogen-containing
gas from the raw material and water through reformation reaction
with the reformation catalyst; a converting device that contains a
converting catalyst and decreases carbon monoxide in the
hydrogen-containing gas through shift reaction with the converting
catalyst; and a first temperature detector that detects a
temperature of the converting catalyst, and the method comprising:
a purging step of purging an interior of the converting device with
the raw material by the raw material supplying device when a
detected temperature of the first temperature detector becomes a
first threshold value, at which deterioration of converting
catalyst with the raw material is suppressed, or lower in a
shutdown operation.
27. The method for operating the hydrogen generating apparatus
according to claim 26, wherein the purging step is performed when a
detected temperature of the first temperature detector is the first
threshold value or lower and is higher than a dew point of a gas in
the converting device.
28. The method for operating the hydrogen generating apparatus
according to claim 26, wherein the hydrogen generating apparatus
comprises a second temperature detector that detects a temperature
of the reformation catalyst, and the purging step is performed when
a detected temperature of the first temperature detector is the
first threshold value or lower, and a detected temperature of the
second temperature detector becomes a second threshold value, at
which deterioration of the reformation catalyst with the raw
material is suppressed, or lower.
29. The method for operating the hydrogen generating apparatus
according to claim 28, wherein the hydrogen generating apparatus
comprises a heating device that heats the reformation catalyst, and
a cooling device that cools the converting catalyst, and the method
comprising a cooling step of, in a shutdown operation, stopping the
heating device and cooling the converting catalyst by the cooling
device in such a manner that the detected temperature of the first
temperature detector becomes the first threshold value or lower at
the time when the detected temperature of the second temperature
detector becomes the second threshold value or lower or before the
time when it becomes the second threshold value or lower.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a U.S. national phase application of PCT
International Patent Application No. PCT/JP2008/001800 filed on
Jul. 4, 2008, claiming the benefit of priority of Japanese Patent
Application No. 2007-187250 filed on Jul. 18, 2007, all of which
are incorporated by reference herein in their entirety.
TECHNICAL FIELD
[0002] The present disclosure relates to a hydrogen generating
apparatus, a method for operating a hydrogen generating apparatus,
and a fuel cell system. More particularly, it relates to a hydrogen
generating apparatus having a converting device that performs shift
reaction of carbon monoxide with a converting catalyst, a method
for operating a hydrogen generating apparatus, and a fuel cell
system.
BACKGROUND ART
[0003] A hydrogen-containing gas is used as an anode gas in a fuel
cell. A steam reforming method is generally employed as a formation
method of the hydrogen-containing gas.
[0004] Specifically, for example, a hydrogen generating apparatus
used in a fuel cell system has a reforming device that generates a
hydrogen-containing gas from a raw material and water through a
steam reforming reaction, and a heating device that feeds heat
required for the steam reforming reaction to the reforming device.
The reforming device is equipped with a reformation catalyst. The
hydrogen generating apparatus is so constituted that a raw material
of a hydrocarbon series, such as natural gas, LPG, naphtha,
gasoline and kerosene, or an alcohol series, such as methanol, and
water are supplied to the reforming device from an external supply
infrastructure, the reforming device is heated with the heating
device to a temperature suitable for the steam reformation reaction
(reformation reaction temperature), and a hydrogen-containing gas
thus generated is delivered from the reforming device.
[0005] In the steam reformation reaction, carbon monoxide (which is
hereinafter referred to as CO) is formed as a by-product, and the
hydrogen-containing gas delivered from the reforming device
contains CO in an amount of approximately 10 to 15%. Remaining
water is also contained as steam. CO contained in the
hydrogen-containing gas poisons an electrode catalyst of a fuel
cell to lower the electric power generation capability, and thus a
hydrogen generating apparatus used in a fuel cell system is
equipped with a unit that decreases the CO concentration in the
hydrogen-containing gas.
[0006] As the method of decreasing the CO concentration, shift
reaction is ordinarily used, in which CO and steam are reacted and
converted to hydrogen and carbon dioxide.
[0007] Accordingly, the hydrogen generating apparatus has a
converting device that performs shift reaction of CO and steam in
the hydrogen-containing gas, and the converting device is equipped
with a converting catalyst. The hydrogen generating apparatus is so
constituted that the hydrogen-containing gas is supplied to the
converting device at a temperature suitable for the shift reaction
(shift reaction temperature), and the hydrogen-containing gas
decreased in CO concentration is discharged from the converting
device. In many cases, the CO concentration in the
hydrogen-containing gas is decreased to approximately 0.5% or less
by the converting device.
[0008] For further decreasing CO, a CO removing device equipped
with a selective oxidation catalyst is provided on the downstream
side of the converting device, and CO in the hydrogen-containing
gas is oxidized by supplying air to the CO removing device, thereby
decreasing the CO concentration in the hydrogen-containing gas to
100 ppm, and preferably to 10 ppm or less. The hydrogen-containing
gas containing hydrogen discharged from the CO removing device as a
major component is supplied to a fuel cell for electric power
generation.
[0009] As the converting catalyst, such a catalyst is used as a
noble metal catalyst, e.g., platinum, ruthenium and rhodium, a
Cu--Zn catalyst and a Fe--Cr catalyst.
[0010] Upon using a Cu--Zn catalyst as the converting catalyst
among these catalysts, the shift reaction proceeds in a reducing
atmosphere. Accordingly, for preventing the catalyst capability
from being deteriorated, it is desirable to suppress the catalyst
from being oxidized, thereby maintaining the reducing atmosphere
even in the shutdown state of the hydrogen generating
apparatus.
[0011] When steam remains inside the converting device in the
shutdown state of the hydrogen generating apparatus, there are
cases where the converting catalyst absorbs water produced by
condensing the steam through a decrease in temperature, and the
absorbed water is evaporated through an increase in temperature
upon the next start-up, thereby disrupting the converting
catalyst.
[0012] Accordingly, such a method is proposed that in the shutdown
operation of the hydrogen generating apparatus, the temperature of
the reformation catalyst is decreased while supplying the raw
material and water, and when the temperature of the reformation
catalyst reaches the prescribed temperature, at which thermal
decomposition of the raw material occurs, (for example, 300.degree.
C. for butane gas) or lower, supply of water is stopped, and the
converting device is purged with the raw material (see, for
example, JP-A-2000-95504). According to the aforementioned shutdown
operation, steam can be purged from the converting device as much
as possible, and the catalyst can be suppressed from being
oxidized.
[0013] Such a method is proposed that in the shutdown operation of
the hydrogen generating apparatus, purge with steam is performed,
and then after the temperature of the reformation catalyst layer is
decreased to a temperature that is equal to or lower than the
temperature, at which thermal decomposition of the raw material
does not occur, and is equal to or higher than the condensation
temperature of steam, the raw material is supplied to the
converting device (see, for example, JP-A-2002-151124).
[0014] In the hydrogen generating apparatus of JP-A-2002-151124,
the reforming device is purged with the raw material, and the raw
material discharged from the reforming device is supplied to the
converting device, thereby purging the converting device with the
raw material. On the other hand, JP-A-2000-95504 discloses such a
constitution that the raw material is supplied directly to the
converting device from the raw material supplying device, thereby
purging the converting device with the raw material independently
from the purge of the reforming device with the raw material (see,
for example, FIGS. 2 and 3 of JP-A-2000-95504).
[0015] The entire disclosure of JP-A-2000-95504 and
JP-A-2002-151124 are incorporated herein by reference in its
entirety.
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0016] JP-A-2000-95504 and JP-A-2002-151124 consider that the raw
material purge is performed at a temperature that is lower than the
temperature, at which thermal decomposition of the raw material
does not occur on the reformation catalyst, and is equal to or
higher than the temperature, at which water is not condensed, but
do not consider the temperature of the converting catalyst on the
raw material purge.
[0017] In the case where the converting device is purged with the
raw material independently as shown in JP-A-2000-95504, the purge
is performed based on the detected temperature of the reforming
device, but the temperature of the converting catalyst is not
considered.
[0018] As described above, the inventors have found that in the raw
material purge in the shutdown operation of the hydrogen generating
apparatus, if the control is performed without consideration of the
temperature of the converting catalyst, there are cases where the
converting catalyst is deteriorated, and in particular, if the raw
material purge is performed when the converting catalyst is at a
high temperature, the converting catalyst is deteriorated. The
details of the phenomenon will be described below with reference to
FIG. 2.
[0019] In view of the aforementioned problems, an object of the
present disclosure is to provide a hydrogen generating apparatus, a
method for operating a hydrogen generating apparatus and a fuel
cell system, in which the deterioration of the converting catalyst
can be further suppressed during the raw material purge in the
shutdown operation.
Means for Solving the Problems
[0020] The 1.sup.st aspect of the present disclosure is a hydrogen
generating apparatus comprising:
[0021] a raw material supplying device that supplies a raw
material;
[0022] a reforming device that contains a reformation catalyst and
generates a hydrogen-containing gas from the raw material through a
reformation reaction with the reformation catalyst;
[0023] a converting device that contains a converting catalyst and
decreases carbon monoxide in the hydrogen-containing gas through a
shift reaction with the converting catalyst;
[0024] a first temperature detector that detects a temperature of
the converting catalyst; and
[0025] a controlling device,
[0026] the controlling device controlling the raw material
supplying device to purge an interior of the converting device with
the raw material when a detected temperature of the first
temperature detector becomes a first threshold value, at which
deterioration of the converting catalyst with the raw material is
suppressed, or lower in a shutdown operation.
[0027] The 2.sup.nd aspect of the present disclosure is the
hydrogen generating apparatus according to the 1.sup.st aspect of
the present disclosure, wherein
[0028] the apparatus comprises a cooling device that cools the
converting catalyst, and
[0029] the controlling device cools the converting catalyst with
the cooling device and performs the control in a shutdown
operation.
[0030] The 3.sup.rd aspect of the present disclosure is the
hydrogen generating apparatus according to the 1.sup.st aspect of
the present disclosure, wherein
[0031] the apparatus comprises a cooling device that cools the
converting catalyst, and
[0032] the controlling device controls the cooling device in such a
manner that the detected temperature of the first temperature
detector becomes the first threshold value or lower before purging
an interior of the reforming device and the interior of the
converting device, with the raw material.
[0033] The 4.sup.th aspect of the present disclosure is the
hydrogen generating apparatus according to the 1.sup.st aspect of
the present disclosure, wherein the controlling device controls the
raw material supplying device to purge an interior of the
converting device with the raw material when a detected temperature
of the first temperature detector is the first threshold value or
lower and is higher than a dew point of a gas in the converting
device.
[0034] The 5.sup.th aspect of the present disclosure is the
hydrogen generating apparatus according to the 1.sup.st aspect of
the present disclosure, wherein
[0035] the apparatus comprises a second temperature detector that
detects a temperature of the reformation catalyst, and
[0036] the controlling device performs the control when a detected
temperature of the first temperature detector is the first
threshold value or lower, and a detected temperature of the second
temperature detector becomes a second threshold value, at which
deterioration of the reformation catalyst with the raw material is
suppressed, or lower.
[0037] The 6.sup.th aspect of the present disclosure is the
hydrogen generating apparatus according to the 5.sup.th aspect of
the present disclosure, wherein
[0038] the apparatus comprises a heating device that heats the
reformation catalyst, and
[0039] a cooling device that cools the converting catalyst, and
[0040] in a shutdown operation, the controlling device stops the
heating device and controls the cooling device in such a manner
that the detected temperature of the first temperature detector
becomes the first threshold value or lower at the time when the
detected temperature of the second temperature detector becomes the
second threshold value or lower or before the time when it becomes
the second threshold value or lower.
[0041] The 7.sup.th aspect of the present disclosure is the
hydrogen generating apparatus according to the 2.sup.nd aspect of
the present disclosure, wherein the cooling device is a cooling
fan.
[0042] The 8.sup.th aspect of the present disclosure is the
hydrogen generating apparatus according to the 6.sup.th aspect of
the present disclosure, wherein the cooling device is a cooling
fan.
[0043] The 9.sup.th aspect of the present disclosure is the
hydrogen generating apparatus according to the 1.sup.st aspect of
the present disclosure, wherein
[0044] the apparatus comprises a cooling device that cools the
converting catalyst, and
[0045] a heating device that heats the reformation catalyst,
[0046] the heating device contains a fuel supplying part that
supplies a fuel for combustion and an air supplying part that
supplies air for combustion, and
[0047] the air supplying part also functions as the cooling
device.
[0048] The 10.sup.th aspect of the present disclosure is the
hydrogen generating apparatus according to the 1.sup.st aspect of
the present disclosure, wherein the converting catalyst contains Cu
and Zn.
[0049] The 11.sup.th aspect of the present disclosure is a fuel
cell system comprising:
[0050] the hydrogen generating apparatus according to the 1.sup.st
aspect of the present disclosure, and
[0051] a fuel cell that generates electric power by using the
hydrogen-containing gas supplied from the hydrogen generating
apparatus.
[0052] The 12.sup.th aspect of the present disclosure is a method
for operating a hydrogen generating apparatus,
[0053] the hydrogen generating apparatus comprising:
[0054] a raw material supplying device that supplies a raw
material;
[0055] a reforming device that contains a reformation catalyst and
generates a hydrogen-containing gas from the raw material and water
through reformation reaction with the reformation catalyst;
[0056] a converting device that contains a converting catalyst and
decreases carbon monoxide in the hydrogen-containing gas through
shift reaction with the converting catalyst; and
[0057] a first temperature detector that detects a temperature of
the converting catalyst, and
[0058] the method comprising a purging step of purging an interior
of the converting device with the raw material by the raw material
supplying device when a detected temperature of the first
temperature detector becomes a first threshold value, at which
deterioration of the converting catalyst with the raw material is
suppressed, or lower in a shutdown operation.
[0059] The 13.sup.th aspect of the present disclosure is the method
for operating the hydrogen generating apparatus according to the
12.sup.th aspect of the present disclosure, wherein the purging
step is performed when a detected temperature of the first
temperature detector is the first threshold value or lower and is
higher than a dew point of a gas in the converting device.
[0060] The 14.sup.th aspect of the present disclosure is the method
for operating the hydrogen generating apparatus according to the
12.sup.th aspect of the present disclosure, wherein
[0061] the hydrogen generating apparatus comprises a second
temperature detector that detects a temperature of the reformation
catalyst, and
[0062] the purging step is performed when a detected temperature of
the first temperature detector is the first threshold value or
lower, and a detected temperature of the second temperature
detector becomes a second threshold value, at which deterioration
of the reformation catalyst with the raw material is suppressed, or
lower.
[0063] The 15.sup.th aspect of the present disclosure is the method
for operating the hydrogen generating apparatus according to the
14.sup.th aspect of the present disclosure, wherein
[0064] the hydrogen generating apparatus comprises a heating device
that heats the reformation catalyst, and a cooling device that
cools the converting catalyst, and
[0065] the method comprising a cooling step of, in a shutdown
operation, stopping the heating device and cooling the converting
catalyst by the cooling device in such a manner that the detected
temperature of the first temperature detector becomes the first
threshold value or lower at the time when the detected temperature
of the second temperature detector becomes the second threshold
value or lower or before the time when it becomes the second
threshold value or lower.
Advantage of the Present Disclosure
[0066] According to the present disclosure, a hydrogen generating
apparatus, a method for operating a hydrogen generating apparatus
and a fuel cell system are provided that can suppress deterioration
in capability of a converting catalyst on raw material purge during
a shutdown operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0067] FIG. 1 is an exemplary schematic illustration showing a
constitution of a fuel cell system in an embodiment of the present
disclosure.
[0068] FIG. 2 is a graph showing temperature characteristics of a
converting catalyst before and after passing a raw material through
the catalyst.
[0069] FIG. 3 is a graph showing temperature transition in a
shutdown operation of a hydrogen generating apparatus in an
embodiment of the present disclosure.
[0070] FIG. 4 is a graph showing temperature transition in a
shutdown operation of a hydrogen generating apparatus in a modified
example of an embodiment of the present disclosure.
[0071] FIG. 5 is a graph showing temperature transition in a
shutdown operation of a hydrogen generating apparatus in a modified
example of an embodiment of the present disclosure.
[0072] FIG. 6 is a cross sectional constitutional view showing an
example of a specific structure of a hydrogen generating apparatus
in an embodiment of the present disclosure.
[0073] FIG. 7 is a schematic illustration showing a constitution of
a fuel cell system in a modified example of an embodiment of the
present disclosure.
DESCRIPTION OF THE REFERENCE NUMERALS AND SIGNS
[0074] 100 hydrogen generating apparatus [0075] 101 raw material
supplying device [0076] 102 raw material supplying path [0077] 103
water supplying device [0078] 104 water supplying path [0079] 111
reforming device [0080] 112 heating device [0081] 113 second
temperature detector [0082] 121 converting device [0083] 122
cooling fan [0084] 123 first temperature detector [0085] 131 CO
removing device [0086] 139a, 139b, 139c hydrogen-containing gas
path [0087] 200 controlling device [0088] 300 fuel cell
DETAILED DESCRIPTION
[0089] A detailed description of the present disclosure will be
described below with reference to the drawings.
Embodiment 1
[0090] FIG. 1 is an exemplary schematic illustration showing a
constitution of a fuel cell system 10 of an embodiment 1 according
to the present disclosure. The fuel cell system 10 of the
embodiment 1 has a hydrogen generating apparatus 100 and a fuel
cell 300.
[0091] The fuel cell (FC) 300 is such an apparatus that uses a
hydrogen-containing gas supplied from the hydrogen generating
apparatus 100 as an anode gas and uses an oxidizing gas, such as
air, supplied separately as a cathode gas, thereby generating
electric power through reaction between them.
[0092] The hydrogen generating apparatus 100 has a reforming device
111, a converting device 121 disposed on the downstream side of the
reforming device 111, and a carbon monoxide removing device (which
is hereinafter referred to as a CO removing device) 131 disposed on
the downstream side of the converting device 121. A raw material
supplying device 101, which is a supplying system of a raw
material, a raw material supplying path 102 connected to the raw
material supplying device 101, a water supplying device 103, which
is a supplying system of water, and a water supplying path 104
connected to the water supplying device 103 are provided.
[0093] The raw material supplying path 102 and the water supplying
path 104 are connected to the reforming device 111. A heating
device 112 that supplies heat to the reforming device 111, and a
second temperature detector 113 that detects the temperature in the
reforming device 111 are provided.
[0094] A cooling fan 122, which is an example of a cooling device
of the present disclosure that cools the converting device 121, and
a first temperature detector 123 that detects the temperature in
the converting device 121 are provided.
[0095] A hydrogen-containing gas path 139a that connects the
reforming device 111 and the converting device 121, a
hydrogen-containing path 139b that connects the converting device
121 and the CO removing device 131, and a hydrogen-containing gas
path 139c that connects the CO removing device 131 and the fuel
cell 300 are provided, and the hydrogen-containing gas generated in
the reforming device 111 is supplied to the fuel cell 300 through
the hydrogen-containing gas paths 139a, 139b and 139c.
[0096] A controlling device 200 that controls the aforementioned
devices is provided. The cooling device is not limited to the
cooling fan 122, and may be a constitution that cools with water,
or a constitution that can cool the converting catalyst with air
delivered by a fan used for combustion in the heating device
112.
[0097] As the raw material, a raw material containing an organic
compound constituted by a carbon element and a hydrogen element is
preferably used, examples of which include a hydrocarbon, such as
natural gas, LPG, naphtha, gasoline and kerosene, or an alcohol
series, such as methanol.
[0098] The reforming device 111 has a reformation catalyst disposed
therein. Steam reformation reaction proceeds with the reformation
catalyst, whereby a hydrogen-containing gas can be generated from
the raw material and steam. Heat required for the steam reformation
reaction is supplied from the heating device 112. As the reforming
catalyst, generally at least one selected from the group consisting
of a noble metal catalyst, such as platinum (Pt), ruthenium (Ru)
and rhodium (Rh), and a nickel (Ni) catalyst is preferably
used.
[0099] The converting device 121 has a converting catalyst disposed
therein. Shift reaction proceeds with the converting catalyst,
whereby hydrogen and carbon dioxide can be generated from carbon
monoxide and water in the hydrogen-containing gas delivered from
the reforming device 111. As the converting catalyst, generally at
least one selected from the group consisting of a noble metal
catalyst, such as Pt, Ru and Rh, a copper-zinc (Cu--Zn) catalyst
and an iron-chromium (Fe--Cr) catalyst is preferably used.
[0100] The CO removing device 131 has a selective oxidation
catalyst disposed therein. Selective oxidation reaction of CO
proceeds with the selective oxidation catalyst, whereby carbon
monoxide in the hydrogen-containing gas after subjecting to shift
reaction can be further decreased. As the selective oxidation
catalyst, a Pt catalyst or a Ru catalyst is preferably used.
[0101] In the embodiment, the fuel cell 300 is a polymer
electrolyte fuel cell (PEFC), and therefore, it is necessary to
further decrease the carbon monoxide concentration with the
selective oxidation catalyst to prevent the catalyst capability of
the PECF from being deteriorated. Accordingly, the CO removing
device 131 may be omitted depending on the destination of the
hydrogen-containing gas. For example, in the case where the fuel
cell 300 is a phosphoric acid fuel cell (PAFC), the CO removing
device 131 may be omitted.
[0102] The heating device 112 is so constituted that an amount of
heat that is required for the steam reformation reaction can be
supplied to the reforming device 111. In the embodiment, the
heating device 112 has a burner for burning a combustible gas, such
as the raw material and the hydrogen-containing gas, an igniting
device, and a gas supplying device, such as a fan and a pump, that
supplies an oxidizing gas, such as air, (which are not shown in the
figures). The heating device 112 is so constituted that the heating
temperature can be controlled by adjusting the supplying amount of
the combustible gas. According to the constitution, the reforming
device 111 can be heated to a temperature suitable for the steam
reformation reaction (reformation reaction temperature).
[0103] The controlling device 200 includes a computer, such as a
microcomputer, and has a function of controlling the raw material
supplying device 101, the water supplying device 103, the heating
device 112 and the cooling fan 122, and is so constituted that the
temperature information from the second temperature detector 113
and the first temperature detector 123 can be acquired.
[0104] The controlling device 200 includes not only a single
controlling device but may also be formed by a group of controlling
units that perform the control by plural controlling units
collaborating with one another. Accordingly, the controlling device
200 may not be constituted by a single controlling device, but may
be so constituted by plural controlling units which are distributed
and which control the hydrogen generating apparatus 100 in
cooperation with each other.
[0105] An example of operation of the hydrogen generating apparatus
100 in an electric power generation operation will be described
with reference to FIG. 1. The operation is performed by controlling
with the controlling device 200.
[0106] The raw material supplying device 101 is controlled to
supply the raw material to the reforming device 111 through the raw
material supplying path 102.
[0107] The water supplying device 103 is controlled to supply water
to the reforming device 111 through the water supplying path 104.
The supplying amount of water is preferably such a flow amount that
provides a steam (molar amount of H.sub.2O molecules in water
supplying amount per unit time)/carbon (molar amount of C atoms in
raw material supplying amount per unit time) ratio of approximately
2.5 to 3.
[0108] The reforming device 111 is heated to a temperature suitable
for the steam reformation reaction (reformation reaction
temperature) with the heating device 112. The heating temperature
is controlled based on the detected temperature of the second
temperature detector 113. In the embodiment, a Ru catalyst is used
as the reformation catalyst, and therefore, it is preferred to heat
with the heating device 112 to a temperature of approximately
650.degree. C. detected by the second temperature detector 113.
[0109] According to the control, in the reforming device 111, a
hydrogen-containing gas is efficiently generated through the steam
reformation reaction from the mixed gas of the raw material and
steam.
[0110] The hydrogen-containing gas is supplied to the converting
device 121, and the carbon monoxide concentration of the
hydrogen-containing gas is decreased through the shift reaction.
The temperature of the converting device 121 is controlled to a
temperature suitable for the shift reaction (shift reaction
temperature). The converting device 121 is so constituted that it
is heated with the heat from the heating device 112 remaining after
heating the reforming device 111, and therefore, the temperature of
the converting device 121 is controlled by adjusting the heat
amount remaining after heating the reforming device 111 by
adjusting the heating amount of the heating device 112 based on the
detected temperature of the first temperature detector 123.
However, the temperature control is not limited to this
constitution, and it is possible to provide a separate heating
device utilizing electric resistance and to utilize external waste
heat.
[0111] In the embodiment, a Cu--Zn converting catalyst is used as
the converting catalyst. The temperature is controlled so that the
temperature detected by the first temperature detector 123 is
approximately 200 to 300.degree. C.
[0112] The hydrogen-containing gas discharged from the converting
device 121 is supplied to the CO removing device 131, thereby
further decreasing the carbon monoxide concentration of the
hydrogen-containing gas through the selective oxidation reaction of
carbon monoxide. The temperature of the CO removing device 131 is
controlled to a temperature suitable for the selective oxidation
reaction (selective oxidation reaction temperature). The CO
removing device 131 is so constituted that it is heated with the
heat from the heating device 112 remaining after heating the
reforming device 111, and therefore, the temperature of the CO
removing device 131 is controlled by adjusting the heat amount from
the heating device 112 remaining after heating the converting
device 121 by adjusting the heating amount of the heating device
112. However, the temperature control is not limited to this
constitution, and it is possible to provide a separate heating
device utilizing electric resistance and to utilize external waste
heat. In the embodiment, the CO removing device 131 is heated to a
temperature within a range of approximately 100 to 200.degree.
C.
[0113] The hydrogen-containing gas delivered from the CO removing
device 131 is supplied as an anode gas to the fuel cell 300 through
the hydrogen-containing gas path 139c. An oxidizing gas, such as
air, is separately supplied as a cathode gas (which is not shown in
the figure) to the fuel cell 300, and the fuel cell 300 generates
electric power through electrochemical reaction. According to the
process, a hydrogen-containing gas that has been sufficiently
decreased in carbon monoxide can be generated by operating the
hydrogen generating apparatus 100, whereby the fuel cell 300 can
perform electric power generation.
[0114] Upon shutting down the fuel cell in the electric power
generation state, the hydrogen generating apparatus is subjected to
a shutdown operation. The shutdown operation of the hydrogen
generating apparatus will be described in detail below, and the
shutdown operation is completed finally after purging the interior
thereof with the raw material, as described in JP-A-2000-95504 and
JP-A-2002-151124. Accordingly, the inventors have investigated as
to whether the passage of the raw material upon the shutdown
operation influences the characteristics of the converting
catalyst.
[0115] The investigation results of the characteristics of the
Cu--Zn converting catalyst used in the converting device 121 of the
embodiment will be described with reference to an experimental
example shown in FIG. 2.
[0116] FIG. 2 is a graph showing the results of a comparison of the
characteristics of the converting catalyst before and after the
passage of the raw material by disposing the converting catalyst in
a fixed bed passage reaction apparatus equipped with an electric
furnace.
[0117] The plots in FIG. 2 are the results (temperature
characteristics) obtained in such a manner that a simulated
hydrogen-containing gas corresponding to the gas after passing
through the reforming device is passed through the converting
catalyst, and the temperature of the converting catalyst is
changed, at which the carbon monoxide concentration in the
simulated hydrogen-containing gas after passing through the
converting catalyst is measured with gas chromatography.
[0118] The converting catalyst used was a commercially available
Cu--Zn catalyst (produced by Sud-Chemie Catalysts, Inc.), and 20 cc
thereof was charged in a reaction tube. The temperature
characteristics of the catalyst were measured by decreasing the set
temperature of the electric furnace supplying heat to the reaction
tube having the converting catalyst charged therein while passing a
simulated hydrogen-containing gas (hydrogen: 57%, carbon monoxide:
9%, carbon dioxide: 8%, steam: 26%) at 300 mL/min.
[0119] The plots for "initial" (white circles) in FIG. 2 show the
temperature characteristics (initial characteristics) measured
under the aforementioned conditions after the converting catalyst
is charged in the reaction tube and subjected to a reduction
treatment.
[0120] The method for passing the raw material for investigating
the influence of the raw material purge will be described.
[0121] After measuring the temperature characteristics, heat was
applied to the converting catalyst with the electric furnace to a
temperature of 300.degree. C., and while maintaining the
temperature, a desulfurized city gas as the raw material was passed
therethrough at a flow rate of 200 mL/min for 100 hours.
[0122] After passing the city gas, the simulated
hydrogen-containing gas was passed through the converting catalyst
to measure the temperature characteristics as similar to the
measurement of the initial temperature characteristics. The results
are shown by the plots for "300.degree. C." (black triangles) in
FIG. 2.
[0123] What is understood from the results will be described
below.
[0124] It is understood from FIG. 2 that in the case where the
catalyst is in the initial state, for example, CO can be decreased
to approximately 0.5 dry % at a catalyst temperature of 200.degree.
C., but after passing the city gas, it can be decreased only to
approximately 8 dry % at the same catalyst temperature. That is, it
shows deterioration of the catalyst.
[0125] The catalyst was then replaced by a fresh one, which was
subjected to a reduction treatment, and the temperature
characteristics of the replaced catalyst were measured, thereby
confirming that the initial characteristics of the replaced
catalyst were equivalent to the aforementioned characteristics
(i.e., the plots for "initial" in FIG. 2) (not shown in the
figure).
[0126] Thereafter, heat was applied to the converting catalyst with
the electric furnace to a temperature of 200.degree. C., and a
desulfurized city gas was passed therethrough at a flow rate of 200
mL/min for 100 hours. Thereafter, the simulated hydrogen-containing
gas was passed through the converting catalyst to measure the
temperature characteristics. The results are shown by the plots for
"200.degree. C." (black rhombuses) in FIG. 2. It is understood from
the results that the decrease in characteristics is suppressed as
compared to the case where the city gas is passed at 300.degree.
C., but the catalyst capability is decreased from the initial
characteristics.
[0127] The catalyst was then replaced and subjected to a reduction
treatment, and the temperature characteristics of the replaced
catalyst were measured. Thereafter, heat was applied to the
converting catalyst with the electric furnace to a temperature of
100.degree. C., and a desulfurized city gas was passed therethrough
at a flow rate of 200 mL/min for 100 hours. Thereafter, the
temperature characteristics were measured. The results are shown by
the plots for "100.degree. C." in FIG. 2. It is understood that
substantially no decrease in characteristics is observed after
passing the city gas at 100.degree. C.
[0128] As described above, the inventors have found from the
results shown in FIG. 2 that upon passing a raw material, the
temperature of the converting catalyst is desirably as low as
possible since deterioration in capability of the converting
catalyst is suppressed.
[0129] Accordingly, upon performing raw material purge in a
shutdown operation after the normal operation at a temperature of
the converting catalyst of 300.degree. C., it is necessary to
consider the temperature of the converting catalyst. Furthermore,
when decrease of the temperature of the converting catalyst does
not proceed before performing the raw material purge, it is
necessary to cool the converting catalyst by any suitable
measure.
[0130] The shutdown operation of the hydrogen generating apparatus
100, which is a characteristic feature of the present disclosure,
will be described, and an example of the method for operating the
hydrogen generating apparatus of the present disclosure will be
described simultaneously.
[0131] FIG. 3 is a schematic illustration showing a graph of
temperature transition detected by the second temperature detector
113 and the first temperature detector 123 in the electric power
generation to the shutdown operation. In FIG. 3, the temperature
detected by the second temperature detector 113 is shown as the
reformation temperature, and the temperature detected by the first
temperature detector 123 is shown as the modification temperature.
The same is applied to FIGS. 4 and 5 described later.
[0132] In the embodiment, the control is so performed during the
electric power generation that the reformation temperature is
650.degree. C., and the converting temperature is 300.degree.
C.
[0133] Upon shutting down electric power generation, the
controlling device 200 stops heating with the heating device 112
and stops supply of the raw material and water by stopping the
operation of the raw material supplying device 101 and the water
supplying device 103. The time when supply of the raw material and
water is stopped corresponds to the time T.sub.0 in FIG. 3.
[0134] When heating with the heating device 112 is stopped, the
temperature of the reformation catalyst is decreased. When the
operation of the raw material supplying device 101 and the water
supplying device 103 is stopped, the flow of the
hydrogen-containing gas heated with the heating device 112 into the
converting device 121 is stopped to decrease the temperature of the
converting catalyst, but it is not directly heated like the
reformation catalyst, and therefore the temperature thereof is
decreased more gradually as compared to the reformation
catalyst.
[0135] Accordingly, such control is performed that the cooling fan
122 is driven immediately after stopping supply of the raw material
and water, thereby cooling the converting catalyst. The control
corresponds to an example of the cooling process of the present
disclosure.
[0136] When the temperature detected by the second temperature
detector 113 becomes the second threshold value, at which the raw
material is not heat-decomposed on the reformation catalyst, (for
example, 400.degree. C.) or lower, and the temperature detected by
the first temperature detector 123 becomes the first threshold
value, at which deterioration of the converting catalyst with the
raw material is suppressed, (for example, 100.degree. C.) or lower,
the operation of the raw material supplying device 101 is started
to start supply of the raw material for purging the
hydrogen-containing gas accumulated in the hydrogen generating
apparatus 100. The time when supply of the raw material is started
corresponds to the time T.sub.1 in FIG. 3. An example of the
temperature, at which deterioration of the converting catalyst with
the raw material is suppressed, in the present disclosure
corresponds to the first threshold value of the embodiment, and an
example of the temperature, at which deterioration of the
reformation catalyst with the raw material is suppressed, in the
present disclosure corresponds to the second threshold value of the
embodiment. The first threshold value set with respect to the
temperature of the converting catalyst may be such a temperature
that deterioration of the converting catalyst with the raw material
can be suppressed, and thus may not be 100.degree. C., but may be,
for example, 200.degree. C. However, in order that the hydrogen
generating apparatus maintains the carbon monoxide concentration in
the hydrogen-containing gas supplied to the fuel cell to 10 ppm
even when the characteristics of the converting catalyst are
deteriorated due to repetition of start and stop, it is preferred
to charge in advance such an amount of the catalyst that takes the
decrease in catalyst characteristics into consideration to some
extent. The temperature of the converting catalyst when the raw
material purge is started, is preferably a temperature higher than
the dew point of the gas supplied to the converting device 121.
[0137] In the embodiment, as shown in FIG. 3, the cooling fan 122
is controlled by the controlling device 200 while monitoring the
detected temperature of the second temperature detector 113 and the
detected temperature of the first temperature detector 123 in such
a manner that the period of time t.sub.k from the stop of the
heating device 112 to the time when the detected temperature of the
second temperature detector 113 becomes the second threshold value
(for example, 400.degree. C.) or lower is substantially equal to
the period of time t.sub.h to the time when the detected
temperature of the first temperature detector 123 becomes the first
threshold value (for example, 100.degree. C.) or lower (see T.sub.1
in FIG. 3). By controlling t.sub.h and t.sub.k to make them
substantially the same as each other, there is no latency time
arising after the reformation catalyst reaches the temperature, at
which the raw material can be supplied thereto, until the
converting catalyst reaches the temperature, at which the raw
material can be supplied thereto, whereby the period of time
required for the shutdown operation can be shortened as much as
possible.
[0138] The period of time t.sub.k from the stop of the heating
device 112 to the time when the temperature of the reformation
catalyst reaches 400.degree. C. is substantially constant, and the
period of time t.sub.k can be obtained in advance by actual
measurement. Accordingly, it is possible that the period of time
t.sub.k obtained by actual measurement is set as a fixed value, and
the controlling device 200 operates the cooling fan 122 while
monitoring the detected temperature of the first temperature
detector 123 and the period of time t.sub.h in such a manner that
the period of time t.sub.k and the period of time t.sub.h are made
substantially equal to each other, or it is also possible that the
controlling method of the cooling fan 122 that makes the period of
time t.sub.k and the period of time t.sub.h substantially equal to
each other is determined in advance by experiment, and the
controlling method is stored as a controlling program in a
recording medium. By operating the cooling fan 122 with the
controlling device 200 based on the controlling program in the
recording medium, such control can be performed so that t.sub.h and
t.sub.k are substantially equal to each other.
[0139] In the embodiment, the cooling fan 122 is controlled with
the controlling device 200 to make the period of time t.sub.k and
the period of time t.sub.h substantially equal to each other, but
they may not be necessarily equal to each other, and the similar
advantage can be obtained by controlling the cooling fan 122 in
such a manner that the detected temperature of the first
temperature detector 123 becomes the first threshold value (for
example, 100.degree. C.) or lower within the period until the
detected temperature of the second temperature detector 113 becomes
the second threshold value (for example, 400.degree. C.) or
lower.
[0140] For example, as shown in FIG. 4, the cooling fan 122 may be
controlled in such a manner that the period of time t.sub.h until
the temperature of the converting temperature becomes the first
threshold value or lower is shorter than the period of time t.sub.k
until the temperature of the reformation catalyst becomes the
second threshold value or lower. However, it is preferred that the
cooling fan 122 is stopped at the time when the temperature of the
converting catalyst detected by the first temperature detector 123
is higher than the dew point of the gas passing on the converting
catalyst and is the third threshold value (for example, 100.degree.
C.) close to the dew point or lower (for example, time
T.sub.5=T.sub.0+t.sub.h), and the raw material is supplied after
the time T.sub.1 of lapsing the period of time t.sub.k from the
time T.sub.0 to the time when the temperature of the reformation
catalyst reaches the second threshold value (for example,
400.degree. C.) or lower. The operation of the cooling fan 122 is
controlled to be stopped when the temperature becomes the third
threshold value or lower because even when the gas supplied to the
converting device 121 is cooled to the dew point or lower, the
effect of suppressing deterioration in the characteristics of the
converting catalyst due to supply of the raw material is not so
changed, and furthermore, there is such a possibility that steam in
the gas supplied to the converting catalyst is condensed on the
catalyst to deteriorate the characteristics of the catalyst.
[0141] Although the period of time required for the shutdown
operation becomes longer than the previous embodiment, the period
of time t.sub.h until the converting catalyst reaches 100.degree.
C. may be controlled longer than the period of time t.sub.k until
the reformation catalyst reaches 400.degree. C., as shown in FIG.
5. In this case, as the time of lapsing the period of time t.sub.h
from the time T.sub.0 is represented by T.sub.3, the supply of the
raw material is started at the time T.sub.3, which is later than
the time T.sub.1 of lapsing the period of time t.sub.k from the
time T.sub.0, and thus the time when the supply of the raw material
is completed becomes the time T.sub.4, which is later than the time
T.sub.2 in FIG. 3.
[0142] In the cooling process of the shutdown operation shown in
FIGS. 3 to 5, the first threshold value and the third threshold
value are the same and are both 100.degree. C., and the operation
of the cooling fan 122 is stopped upon starting the raw material
purge. However, for example, it is possible that the first
threshold value is 200.degree. C. and the third threshold value is
100.degree. C., and in this case where the first threshold value is
larger than the third threshold value, the cooling operation with
the cooling fan 122 may be continued during the raw material purge
within the period until the temperature of the converting catalyst
becomes the third threshold value or lower.
[0143] In the cooling process after the time T.sub.0 when the
shutdown operation of the hydrogen generating apparatus is started,
not only the converting catalyst is cooled with the cooling fan
122, but also a unit for cooling the reformation catalyst may be
provided, and the reformation catalyst may be simultaneously cooled
with the cooling unit. For example, a fan may be provided on the
heating device 112, and air may be supplied with the fan to cool
the reformation catalyst.
[0144] A specific constitution of the hydrogen generating apparatus
100 having the heating device 112 equipped with a fan will be
described below.
[0145] FIG. 6 is a cross sectional constitutional view of the
hydrogen generating apparatus 100. The hydrogen generating
apparatus 100 is in a cylindrical form, and has a combustion space
12 having a burner 11 disposed therein, and plural annular spaces
constituted by plural pipes disposed concentrically with the
combustion space 12 as the center. The plural annular spaces means
a first annular space 13 formed outside the combustion space 12
containing the burner 11, a second annular space 14 formed outside
the first annular space 13, a third annular space 15 formed outside
the second annular space 14, and a fourth annular space 16 formed
above the third annular space 15.
[0146] An air supplying part 17 having a fan for supplying air for
combustion to the burner 11, and a fuel supplying part 18 that
supplies a combustible gas, which is an example of the fuel of the
present disclosure, to the burner 11 are provided, and the heating
device 112 equipped with a fan is constituted by the burner 11, the
air supplying part 17 and the fuel supplying part 18. The raw
material supplying part 101 may function as the fuel supplying part
18, the fuel supplying part 18 may be so constituted that off-gas
from the fuel cell 300 is supplied.
[0147] The second annular space 14 is formed in such a manner that
the width of the lower part of the annular space is larger than the
upper part of the annular space, and the reformation catalyst is
charged in the lower part of the annular space to constitute the
reforming device 111.
[0148] The third annular space 15 is formed in such a manner that
the width of the upper part of the annular space is larger than the
lower part of the annular space, and the converting catalyst is
charged in the upper part of the annular space to constitute the
converting device 121. In the third annular space 15, the fourth
annular space 16 is formed above the converting device 121, and the
selective oxidation catalyst is charged in the fourth annular space
16 to constitute the CO removing device 131.
[0149] The raw material supplying path 102 shown in FIG. 1 is
connected to the upper part of the second annular space 14, the
second annular space 14 and the third annular space 15 are
connected at the lower part, the third annular space 15 and the
fourth annular space 16 are connected at the upper part, and the
hydrogen-containing gas path 139c to the fuel cell is connected to
the lower part of the fourth annular space 16.
[0150] Accordingly, the raw material supplied from the raw material
supplying path 102 moves downward in the second annular space 14
through the reforming device 111, then moves upward in the third
annular space 15 through the converting device 121, then moves
downward in the fourth annular space 16 through the CO removing
device 131, discharged from the hydrogen generating apparatus 100,
and directed to the fuel cell 300 through the hydrogen-containing
gas path 139c. In the upper annular space of the second annular
space 14, a wall 19 is formed as running downward and moving in the
circumferential direction, thereby heating the supplied raw
material sufficiently with heat from the burner 11.
[0151] The burner 11 is disposed to form a flame 11a directed
downward, and an exhaust gas formed through combustion with the
burner 11 moves from the lower part of the combustion space 12 to
the first annular space 13, moves upward in the first annular space
13, and discharged outside the hydrogen generating apparatus 100
from the upper part of the first annular space 13 through an
exhaust gas outlet 20. The reforming device 111, the converting
device 121 and the CO removing device 131 are heated with the
combustion heat conducted through the chassis, thereby performing
reaction in each of them.
[0152] The water supplying path 104 is wound around the CO removing
device 131 and then, connected to the raw material supplying path
102. The connecting part thereof is shown by 104a in the figure.
Water flowing in the water supplying path 104 is heated with the CO
removing device 131 upon flowing around the CO removing device
131.
[0153] A cooling air flow path 22 for cooling the converting device
121 is formed around the converting device 121, and a cooling fan
122 for taking cooling air into the cooling air flow path 22, and a
flow outlet 23 for discharging air from the cooling air flow path
22 are provided.
[0154] The first temperature detector 123 and the second
temperature detector 113 described in FIG. 1 are shown in FIG. 6,
and the second temperature detector 113 is disposed on the
downstream side of the reformation catalyst.
[0155] While omitted in FIG. 1, an air supplying part 132 that
supplies air as an oxidizing agent used for selectively oxidizing
CO in the CO removing device 131 is provided between the converting
device 121 and the CO removing device 131.
[0156] In the hydrogen generating apparatus 100 having the
aforementioned constitution, for example, upon stopping the heating
device 112 at the time T.sub.0 in FIGS. 3 to 5, only supply of the
raw material from the fuel supplying part 18 is stopped, but supply
of air from the air supplying part 17 is continued. Control is so
performed that the raw material supplying device 101 and the water
supplying device 103 are stopped simultaneously with the stop of
the supply of the fuel, and the cooling fan 122 is driven.
[0157] The reforming device 111 is cooled and the converting device
121 is also cooled by passing air supplied from the air supplying
part 17 through the combustion space 12 and the first annular space
13, and the converting device 121 is further cooled with air
supplied from the cooling fan 122 to the cooling air flow path
22.
[0158] The period of time for cooling the catalysts can be
shortened by this constitution, and thus the shutdown time and the
shutdown energy can be decreased. In the case where cooling of the
converting catalyst has priority, the operation of the air
supplying part 17 may be stopped simultaneously with the stop of
the cooling fan 122 described with reference to FIGS. 3 to 5.
[0159] The supply of the raw material and water is stopped in the
shutdown operation, but only the supply of the raw material may be
stopped to purge with steam. In this case, at the time when the
reformation catalyst reaches 400.degree. C. and the converting
catalyst reaches 100.degree. C., the supply of water is stopped,
and the supply of raw material is started.
[0160] In the embodiment, such a cooling step is exemplified that
the cooling operation is accelerated with the cooling fan 122 in
the shutdown operation of the hydrogen generating apparatus, but it
is possible that the converting catalyst is cooled by spontaneous
cooling without any special cooling unit like those described the
above, and the supply of the raw material is started with the raw
material supplying device 101 in the case where the detected
temperature of the first temperature detector 123 becomes the first
threshold value or lower.
[0161] In the case where the converting catalyst is cooled without
the cooling fan 122, the cooling air flow path 22 and the flow
outlet 23 provided, such control may be performed that the
converting catalyst is cooled indirectly by only stopping the
supply of the fuel from the fuel supplying part 18 and continuing
the supply of air from the air supplying part 17 in the shutdown
operation as described above in the hydrogen generating apparatus
100 shown in FIG. 6. The air supplying part 17 in this case
corresponds to an example of the air supplying part that also
functions as the cooling device of the present disclosure. In this
constitution, the cooling fan 122 is not necessarily provided,
thereby reducing the cost. The operation of the air supplying part
17 may be controlled as similar to the cooling fan 122 shown in
FIGS. 3 to 5.
[0162] The converting catalyst may be cooled by spontaneous cooling
without acceleration of cooling with the combustion fan provided in
the heating device 112. In this case, the control may be performed
as shown in FIGS. 3 to 5 based on the times when the reformation
catalyst and the converting catalyst reach the threshold values,
respectively.
[0163] In FIG. 6, the reforming device 111, the converting device
121 and the CO removing device 131 are disposed in one vessel, but
they may be disposed independently in separate vessels, and in this
case, air aspirated with the fan provided in the heating device 121
is supplied to the converting device 121, whereby the air supplying
part 17 can function as the cooling fan 122.
[0164] In the embodiment, the supplying amount of the raw material
is set to such a flow amount that can sufficiently purge the
hydrogen-containing gas accumulated in the hydrogen generating
apparatus 100 for purging the interior of the hydrogen generating
apparatus 100 with the raw material, and for example, the raw
material is supplied at a flow rate of 1 NL/min for 10 minutes. The
shutdown operation is completed after stopping the supply of the
raw material, and the operation standby state occurs. The time when
the shutdown operation is completed corresponds to the time T.sub.2
in FIGS. 3 and 4 and the time T.sub.4 in FIG. 5.
[0165] The process of supplying the raw material is an example of
the purging process of the present disclosure, and the similar
advantages as above can be obtained in such a manner that the
supply of the raw material is started in the case where the
detected temperature of the first temperature detector 123 is the
first threshold value or lower in the hydrogen generating apparatus
that is so constituted that the hydrogen-containing gas accumulated
at least in the converting device 121 is purged with the raw
material in the shutdown operation.
[0166] The hydrogen generating apparatus that is so constituted
that the hydrogen-containing gas accumulated at least in the
converting device 121 is purged with the raw material will be
described below. FIG. 7 is a constitutional view showing a fuel
cell system 30 using such a hydrogen generating apparatus 400. The
fuel cell system 30 shown in FIG. 7 is different from the fuel cell
system 10 in FIG. 1 in such a point that a raw material supplying
bypass path 140 is provided to connect between the
hydrogen-containing gas path 139a and the raw material supplying
path 102 with the reforming device 111 bypassed. A three-way valve
141 provided on the raw material supplying path 102 at the
branching point to the raw material supplying bypass path 140, and
a shutoff valve 142 is provided on the hydrogen-containing gas path
139a on the upstream side of the merging point with the raw
material supplying bypass path 140. During electric power
generation, the three-way valve 141 is so controlled that the side
of the raw material supplying bypass path 140 is closed, and the
side of the reforming device 111 is opened, thereby preventing the
raw material gas from being supplied directly to the converting
device 121.
[0167] In the fuel cell system 30, irrespective of the temperature
state of the reformation catalyst, only the converting device 121
can be purged with the raw material without the reforming device
111 in the case where the temperature of the converting catalyst
becomes the first threshold value or lower in the shutdown
operation.
[0168] For example, as shown in FIG. 4, at the time T.sub.5 when
the temperature of the converting catalyst becomes the first
threshold value or lower before lapsing the period of time t.sub.k
until the temperature of the reformation catalyst becomes the
second threshold value or lower, the raw material supplying device
101 is driven in the state where the cooling fan 122 is stopped,
the three-way valve 141 is switched to the raw material supplying
bypass path 140 side, and the shutoff valve 142 is closed, whereby
only the interior of the converting device 121 can be purged with
the raw material without raw material purge of the reforming device
111 performed.
[0169] Accordingly, there is no necessity of allowing the
converting device 121 to stand until the time T.sub.1 when the
temperature of the reformation catalyst becomes the second
threshold value or lower shown in FIG. 4, and thus occurrence of
condensation of steam due to spontaneous cooling in the converting
device 121 after stopping the cooling fan 122 can be suppressed. It
is more preferred that at the time when the temperature of the
reformation catalyst becomes the second threshold value or lower,
the three-way valve 141 is switched to the reforming device 111
side, and the shutoff valve 142 is opened to purge the interior of
the reforming device 111.
[0170] The reforming device 111, the converting device 121 and the
CO removing device 131 in the fuel cell system 30 shown in FIG. 7
may be provided in one vessel, or may be disposed independently in
separate vessels.
[0171] As described above, in the hydrogen generating apparatus and
the fuel cell system having the same of the embodiment, the
converting catalyst is cooled in the shutdown operation, and the
purging operation with the raw material is performed when the
converting catalyst becomes the first threshold value or lower
where deterioration of the converting catalyst is suppressed,
whereby the raw material can be prevented from being passed through
the converting catalyst that is in a high temperature state, and
therefore, deterioration of the catalyst capability of the
converting catalyst can be suppressed. Accordingly, CO in the
hydrogen-containing gas can be stably decreased even when the
hydrogen generating apparatus is repeatedly started and
stopped.
INDUSTRIAL APPLICABILITY
[0172] The hydrogen generating apparatus, the method for operating
a hydrogen generating apparatus and the fuel cell system of the
present disclosure have advantages such as, but not limited to,
that in the raw material purge in the shutdown operation,
deterioration in capability of the converting catalyst can be
suppressed, and are useful as a hydrogen generating apparatus, a
method for operating a hydrogen generating apparatus and a fuel
cell system.
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